The U.S. Chemical Safety Board says it will move forward with a full investigation into Monday’s fatal gas well explosion near Quinton, Oklahoma. Five workers were killed in the blast, which was followed by a fire that destroyed the drill site.

Seventeen workers survived. Most had no or minor injuries; one was flown to a hospital in Tulsa for treatment.

The bodies of the victims were not recovered until a day after the incident.

The two CSB already on the scene have been gathering facts the CSB needed to make a decision regarding the scope of the investigation. The investigators arrived on site Wednesday morning and met with the lease holder for the well and the drilling operator. They will also meet with well service providers and the well site consultant company that had employees on site at the time of the incident.

“Evidence preservation and collection is the initial focus of the investigation,” according to a statement by the CSB.

The CSB is an independent, non-regulatory federal agency whose mission is to drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the President and confirmed by the Senate.

CSB investigations examine all aspects of chemical incidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems. For more information, contact public@csb.gov.